1. Field of the Invention
The present invention relates to a liquid crystal display device.
2. Description of the Related Art
There has been known a liquid crystal display device in which a pair of substrates are arranged to face each other in an opposed manner with liquid crystal therebetween, each one of pixel regions formed on a liquid-crystal-side of one substrate includes a pixel electrode and a counter electrode thereon and the optical transmissivity of the liquid crystal is controlled by generating an electric field between the pixel electrode and the counter electrode.
With respect to such a liquid crystal display device, there has been known a liquid crystal display device in which the above-mentioned respective electrodes are arranged by way of an insulation film, wherein one electrode is formed on the whole region of a center portion in the inside of the pixel region, while another electrode is formed as a group of electrodes which are overlapped to one electrode and have a so-called comb-teeth shape. Further, these electrodes are formed of a light transmitting conductive layer.
Such a liquid crystal display device is disclosed in JP-A-2002-90781 (or corresponding United States patent U.S. Pat. No. 6,562,645), for example.
Further, in JP-A-2000-338462, there has been disclosed a liquid crystal display device having the constitution in which a first video signal transmitted from the first drain signal line is supplied to one electrode through the first thin film transistor which is turned on in response to a scanning signal transmitted from a gate signal line, and a second video signal transmitted from the second drain signal line is supplied to another electrode through the second thin film transistor which is turned on in response to the above-mentioned scanning signal.
In the liquid crystal display device having such a constitution, two drain signal lines are arranged with respect to two thin film transistors formed in one pixel, wherein one voltage from one drain signal line is applied to one thin film transistor and another voltage from another drain signal line is applied to another thin film transistor. Here, one voltage assumes a positive pole and another voltage assumes a negative pole and these voltages constitute voltages in one frame period.
Due to such an operation, the differential voltage between the voltage of one electrode and the voltage of another electrode inside the pixel is applied to the liquid crystal. Further, to enable the AC driving of the liquid crystal voltage, the polarities of one electrode and another electrode are exchanged in the next frame period.
Due to such a constitution, compared to an in-plane switching type liquid crystal display device which arranges a thin film transistor in one pixel and in which the potential of a pixel electrode which is connected to the thin film transistor is, in a state that a potential of another electrode is fixed, subjected to AC driving with respect to the fixed voltage, the AC differential voltage can be halved.
In view of the above, it is possible to decrease the driving voltage of the liquid crystal and hence, the liquid crystal display device of low power consumption can be obtained.